(a) Field of the Invention
The present invention relates to a microphone, and more particularly, to a microphone that outputs a uni-directional signal to improve sensitivity.
(b) Description of the Related Art
In general, a microphone, which is an apparatus converting voice into an electrical signal, has gradually miniaturized in recent years, and consequently, the microphone using micro electro mechanical system (MEMS) technology has been developed.
The above-mentioned MEMS microphone has advantages of tolerance to heat and humidity as compared to a conventional electric condenser microphone (ECM), and may be miniaturized and integrated with a signal processing circuit.
The MEMS microphone (hereinafter, simply referred to as a microphone) is classified into a capacitive type and a piezoelectric type.
First, the microphone of the capacitive type is configured as a fixed membrane and a vibration membrane, and when external sound pressure is applied to the vibration membrane, a capacitance value is changed while an interval between the fixed membrane and the vibration membrane is changed. In this case, the sound pressure is measured by using the capacitance value.
On the other hand, the microphone of the piezoelectric type is configured as only the vibration membrane, and when the vibration membrane is deformed by external sound pressure, the electrical signal is generated by a piezoelectric effect, such that the sound pressure is measured.
In addition, the microphone is classified into an omnidirectional microphone and a directional microphone depending on directional characteristics, and the directional microphone is classified into a bi-directional microphone and a uni-directional microphone.
Here, the bi-directional microphone performs a reproduction for front and rear incident sounds and exhibits attenuation characteristics for sound which is incident at a lateral angle, such that a polar pattern indicating input sensitivity of all directions on the basis of a diaphragm of the microphone is indicated in a figure of eight.
Since the bi-directional microphone has suitable near field characteristics, it is used as a microphone for an announcer of a stadium in which ambient noise is loud.
On the other hand, the uni-directional microphone maintains an output value in response to wide front incident sound and exhibits attenuation characteristics for rear incident sound, thereby improving a signal to noise (S/N) ratio for a front sound source. It is characterized that the uni-directional microphone is suitable for use as an equipment for recognizing a voice due to good articulation.
However, the conventional directional microphone as described above uses a scheme that implements directional characteristics using two omnidirectional sound devices.
This is a scheme that obtains directional characteristics by delaying sound input to the two sound devices using a digital signal processor (DSP), and there are problems that costs are increased due to an addition of a corresponding block in the digital signal processor and a size is also increased.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.